Most base oils which are used as lubricating oils, such as engine oils or automatic transmission fluids, require the addition of additives to improve the performance of the lubricating oil and/or to reduce the friction and wear of the moving parts of a vehicle that rub together. These additives are generally classified as ones that influence the physical and chemical properties of the base fluids or affect primarily the metal surfaces by modifying their physicochemical properties. One such additive is an anti-wear agent that is used to reduce wear of metal components.
When General Motors Corporation (GM) upgraded its DEXRON®-III specification, several test procedures and limits were revised, including the wear limit. Previously the maximum weight loss accepted by GM was 15 mg. In the new specification, GM reduced this limit to 10 mg weight loss maximum. Not all anti-wear additive compositions provide suitable wear inhibition to meet the new GM specifications. Also some wear inhibitors may cause copper corrosion.